- Local anesthetics are drugs that cause reversible loss of sensation in a restricted area of the body when applied topically or injected locally. They work by blocking nerve conduction without structural nerve damage. - Early uses of local anesthetics included chewing cocoa leaves for pain relief in Peru and spinal/epidural anesthesia developed in the late 19th century. Common types include amide drugs like lidocaine, bupivacaine, and ropivacaine as well as ester drugs like cocaine and tetracaine. - Local anesthetics can be administered via various techniques including infiltration, nerve blocks, epidural/spinal anesthesia, intravenous regional anesthesia, and topical application. Factors like drug properties, dosage,

1. Local Anaesthetics
- Dr Nikita Ingale
- JR2
- Dept of Pharmacology
- GMCH Nagpur
PG GUIDE
-Dr Vijay Motghare
-Professor & head
-Dept of Pharmacology
-GMCH Nagpur

2. History
- Natives of Peru, in painful surgical procedures
chewed leaves of cocoa plant and let their saliva flow
into cuts, thus anaesthetic properties were invented
- Leonard corning was first to obtain epidural anaesthesia with cocaine
- Auguste bier tested first spinal anaesthesia in 1898, in his own spinal cord
- Henrich brown introduced use of epinephrine with solution of cocaine

3. Introduction
- Local anaesthetics are drugs which on topical application or local injection cause
reversible loss of sensory perception, pain, in a restricted area of the body.
- They block conduction of nerve without any structural damage.
- sensory and motor impulses are interrupted when LA is applied to a mixed nerve,
resulting in muscular paralysis and loss of autonomic control

4. Susceptibility of nerve fibres
Heavy
Myelinated A
alpha beta
gamma
Myelinated
small A delta
fibres
myelinated B
fibres
Unmyelinated C
fibres
Blocked firstBlocked firstBlocked last Blocked second
recovery

5. Chemical classification
Amides Esters Miscellaneous
- LONG ACTING >180 mins
- [bupivacine ropivacaine]
- INTERMEDIATE ACTING
- 60-120 mins
- [ lidocaine, prilocaine]
- LONG ACTING . 180 mins
[ tetracaine]
- INTERMEDIATE ACTING
- 60-120 mins
- [cocaine]
- SHORT ACTING 30 – 60 mins
- [procaine]
Pramoxine
Dyclonine
Oxethazaine

6. Depending on sources
Natural
Synthetic
nitrogenous Miscellaneous
cocaine benzyl alcohol
Clove oil
phenol
Synthetic non
nitrogenous
Para amino
benzoic acid
QuinoloneAcetanilide
Procaine Lignocaine Chinchocaine

7. On mechanism of action
Specific action
on nerves
Freezing of
tissues
Protoplasmic poison
- Esters
- Amides
- Alcohols
- Ethyl chloride
- Methyl cholride
Carbolic acid

8. Chemical structure
ESTER
AMIDE

9. Mechanism of action

10. Mechanism of action

11. Pharmacokinetics
- Depends on presence of ester or amides
- Esters  metabolized by plasma pseudocholinesterase  rapid hydrolized 
short duration of action
- Amides  metabolized by dealkylation  slow hydrolized  longer duration of
action
- Hypersensitivity more with esters than amides

12. Adverse Effects
1] Blood = prilocaine large doses  accumlation
of metabolite orthotoluidine  converts Hb to methaemoglobin
2] CNS = low doses  tongue numbness, headche
high doses  muscular twitchings, convulsions
cocaine  long lasting euphoria, drug dependance
3]CVS = block sodium channels  depress pacemaker activity
cardiotoxicity by bupivacaine
4] allergic reactions

13. Drug interactions
- Hypertensive pts receiving propranol should be given lidocaine and adrenaline
combination with care
-Alcohol intoxicated needs a higher dose of lidocaine + adrenaline combination for
getting anesthetic effect
-Patients on digoxin due to cardiac failure to be given adrenaline + lidocaine with
care
-In coronary care units, large dose infusion of lidocaine iv for ventricular arrythmias,
coadministration of propranol can cause lidocaine toxicity

14. Action of pH on LA action
- Action is Strongly pH dependant , more at alkaline pH and less at acidic pH
- Less active in infected tissues, due to acidic extracellular pH
- Being weak bases, remains unionised in basic medium and ionised in acidic
medium
- Unioinised form is required for diffusion through axonal membrane, once inside
the axon it gets ionised and binds to the LA receptors

15. Prolongation of action by vasoconstrictors
- Addition of a vasoconstrictor, e.g. adrenaline (1:50,000 to 1:200,000):
- Prolongs duration of action of LAs by decreasing their rate of removal from the
local site into the circulation
- Reduces systemic toxicity of LAs: rate of absorption is reduced
- Provides a more bloodless field for surgery.
- Increases the chances of subsequent local tissue edema and necrosis as well as
delays wound healing by reducing oxygen supply

16. TYPES OF LOCAL
ANAESTHESIA

17. TECHNIQUES OF LA
TOPICAL
CONDUCTION
INFILTRATION
CENTRAL
NERVE BLOCK
INTRAVENOUS
REGIONAL
BLOCKS
SPINAL EPIDURALNERVEFIELD

18. Topical anaesthesia
- It is produced by topical application of a surface
anaesthetic to mucous membranes and abraded skin.
- Only the superficial layer is anaesthetised and there is no loss of motor function.
- Onset and duration depends on the site, the drug, its concentration and form, e.g.
lidocaine (10%) sprayed in the throat acts in 2–5 min and produces anaesthesia
for 30–45 min.

19. Topical anaesthesia
- Throat , cornea, mouth mucosa, nose, pharynx, urethra are easily anesthetised
- These are also used to relieve pain in fissures and facilitate endoscopic
procedures
- Eg = lidocaine 2.5%, eutectic mixture, tetracaine, benzocaine

20. Topical anaesthesia

21. Infiltration anaesthesia

22. Infiltration anaesthesia
- Dilute solution of LA is infiltrated under the skin in the
area of operation—blocks sensory nerve endings.
- Onset of action is almost immediate and duration is shorter
- Uses =. incisions, excisions, hydrocele, herniorrhaphy
- Lidocaine 1-2%, bupivacaine 0.25%, ropivacaine 1%

23. Conduction anaesthesia
Field block
-It is produced by injecting the LA subcutaneously in a manner that all nerves coming to a particular
field are blocked eg scalp and ant abdomen
-Larger area of 5–10 cm can be anaesthetised with lesser drug compared to infiltration.
-Lidocaine 1-2%, bupivacaine 0.25%, ropivacaine 1%

24. Conduction anaesthesia
FIELD BLOCK

25. Conduction anaesthesia
Nerve block
- It is produced by injecting the LA around the appropriate nerve trunks or
plexuses.
- Muscles supplied by the injected nerve/plexus are paralysed.
- The latency of anaesthesia depends on the drug and the area to be
covered by diffusion
- Frequently performed nerve blocks are—lingual, intercostal, ulnar,
sciatic, femoral, brachial plexus, trigeminal, facial, phrenic, etc.—used
for tooth extraction, operations on eye, limbs, abdominal wall, fracture
setting, trauma to ribs, neuralgias
- Lidocaine 2% = intermediate acting
- Bupivacaine 0.25%= long action

26. Conduction anaesthesia
Nerve block

27. Central block anaesthesia
spinal anesthesia
- Injected in the subarachnoid space between L2–3 or L3–4
-The level of anaesthesia depends on the volume and speed of injection, specific gravity
of drug solution and posture of the patient
-USES- the lower limbs, pelvis, lower abdomen, obstetric procedures, caesarean
section
-Choice of the LA for spinal anaesthesia primarily depends on the nature and duration
of the operative procedure.

28. Central block anaesthesia
spinal anesthesia
Advantages of spinal anaesthesia
(i) It is safer.
(ii) Produces good analgesia and muscle relaxation without loss of consciousness.
(iii) Cardiac, pulmonary, renal disease and diabetes pose less problem.
Complications of spinal anaesthesia
1] Respiratory Paralysis 2] Hypotension
3] Headache 4 Cauda Equina Syndrome
5] Septic Meningitis

29. Central block anaesthesia
Epidural anesthesia
THORACIC LUMBAR CAUDAL
- Lidocaine (1–2%) and bupivacaine (0.25– 0.5%) are popular drugs for epidural
anaesthesia
- Technically epidural anaesthesia is more difficult than spinal anaesthesia and
relatively larger volumes of drug are needed. Consequently, blood concentrations of
the LA are higher.
- Cardiovascular complications are similar to that after spinal anaesthesia, but
headache and neurological complications are less likely
- Greatest separation between sensory and motor block is obtained by use of 0.25%
bupivacaine. This is especially valuable for obstetric purposes (mother can
participate in labour without feeling pain)

30. EPIDURAL AND SPINAL ANESTHESIA
Central block anaesthesia

31. Intravenous
regional anaesthesia
- It consists of injection of LA in a vein of a tourniquet occluded limb such that the
drug diffuses retrograde from the peripheral vascular bed to nonvascular tissues
including nerve endings.
- Regional analgesia is produced within 2–5 min and lasts till 5–10 min after
deflating the tourniquet which is kept inflated for not more than 15–60 min to
avoid ischaemic injury.

32. Intravenous
regional anaesthesia

33. Cocaine
- It is a natural alkaloid from leaves of Erythroxylon coca
- Cocaine is a good surface anaesthetic and is rapidly absorbed from buccal
mucous membrane
- should never be injected it is a protoplasmic poison and causes tissue necrosis.
- Causes CNS stimulation with effect on mood and behaviour. Induces a sense of
well being, delays fatigue .In susceptible individuals it produces a state referred
to as ‘high’ leading to strong psychological but little physical dependence.

34. Cocaine
- only indication for cocaine was in ocular anaesthesia.
- As it causes constriction of conjunctival vessels, clouding and rarely sloughing of
cornea (due to drying and local tissue toxicity), commonly not used
- S/E = psychological dependance, bradycardia, rise in bp, nausea vomiting

35. Procaine
- It is the first synthetic local anaesthetic introduced in 1905.
- Procaine forms poorly soluble salt with benzyl penicillin; procaine penicillin
injected i.m. acts for 24 hours due to slow absorption from the site of injection.
- Amide derivative procainamide is used as IA group of anti arrhythmics
- S/E = vasodilation, bradycardia, hydrolysed to PABA so antagonises action of
sulphonamides

36. Prilocaine
- It is similar to lidocaine but does not cause vasodilatation ,
- lower CNS toxicity due to larger volume of distribution.
- It has been used mainly for infiltration, nerve block and intravenous regional
anaesthesia.
- EUTECTIC MIXTURE
- S/E= One of its metabolites, Orthotoluidine, has potential to cause
methaemoglobinaemia.

37. Tetracaine
- A highly lipid- soluble PABA ester, more potent and
highly lipid soluble
- Used for topical application to the eye, nose, throat,
tracheobronchial tree.
- Preferred for ocular anaesthesia, as it neither constricts pupil nor paralyses
accommodation
- S/E = PABA derivative so may antagonise sulphonamides

38. Benzocaine
- Topical anesthetic
- Preparations like ointments, lozenges, suppositories for ulcers, rectal area
- Poor penetration through mucous membrane, least toxic
- Too toxic to be used as injection
Oxethazaine
- Surface anesthetic
- Strongly basic drug, so unionised in acidic medium, used in acidic conditions
like gastritis, heart burns

39. Lignocaine
- It is a versatile LA, good both for surface application
like jelly, viscous solution
- Vasodilatation occurs in the injected area. It is used for surface application,
infiltration, nerve block, epidural, transdermal patch, spinal and intravenous
regional block anaesthesia.
- CNS side effects are dizziness, paraesthesias, euphoria
- Overdose causes muscle twitching, convulsions, cardiac arrhythmias, fall in BP,
coma and respiratory arrest

40. Bupivacaine
- A potent and long-acting amide- linked LA
- used for infiltration, nerve block, epidural and spinal
anaesthesia of long duration.
- A 0.25–0.5% solution injected epidurally produces adequate analgesia
- [ sensory> motor block]
- popular in obstetrics (mother can actively cooperate in vaginal delivery) and for
postoperative pain relief by continuous epidural infusion
- S/E = Prolongs QTc interval, ventricular tachycardia , should not be used for
intravenous regional analgesia.

41. Ropivacaine
- A newer bupivacaine congener, equally long acting
but less cardiotoxic and more motor sparing
- It blocks A and C fibres (involved in pain transmission) more completely thanδ
A fibres which control motor function.β
- Continuous epidural ropivacaine is being used for relief of postoperative and
labour pain.
- Used for infiltration, epidural and regional anaesthesia

42. Future devolopments
- Drug delivery systems-
- Sustained drug delivery systems are under efforts, that will slowly release
anesthetics without a catheter
- No chances of systemic toxicity or risks of intravascular injections
- Encapsulating LA into microspheres, liposomes, microparticles is under efforts

43. Summary

44. Summary

45. Summary

46. References
1) HL Sharma & KK Sharma. Local anesthetics sharma and sharma’s
principles of pharmacology.3rd
edition.hyderabad,Paras Medical
Publisher;2017.p216-26
2) Betram G. Katzung Anthony J.Trevor. Local anesthetics Basic and
Clinical Pharmacology13th
edition.New delhi, Mc Graw Hill Education
Edition;2015.p616-32
3)Goodman, L., Gilman, A. and Brunton, L. 13th
edition, Goodman &
Gilman's manual of pharmacology and therapeutics. Local anaesthetics
New York: McGraw-Hill Medical. P1023-47

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By Dr Shubhangi Gawade